InGaN-BASED LASER DIODES

UV InGaN and GaN single-quantum well structure light-emitting diodes (LEDs) were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. When the emission wavelength of UV InGaN LEDs was shorter than 380 nm, the external quantum efficiency (EQE) of the LED on ELOG was much higher than that on sapphire, but only for highcurrent operation. At low-current operation, both LEDs had the same EQE. When the active layer was GaN, the EQE of the LED on sapphire was much lower than that on ELOG even for lowand high-current operations due to the lack of localized energy states formed by fluctuations in indium composition. In order to improve the lifetime of the laser diodes (LD), ELOG had to be used because the operating current density of the LD is much higher than that of the LED. A violet InGaN multi-quantum-well/GaN/AlGaN separate confinement-heterostructure LD was grown on ELOG on sapphire. The LDs with cleaved mirror facets showed an output power as high as 40 mW under room-temperature continuous-wave (CW) operation. The stable fundamental transverse mode was observed at an output power of up to 40 mW. The estimated lifetimes of the LDs at a constant output power of 10 mW and 30 mW were more than 2,000 and 500 hours respectively, during CW operation at an ambient temperature of 60°C. Cutting Edge